龍(long)卷風是(shi)一種少見(jian)的(de)(de)局地(di)性、小尺度(du)、突發性的(de)(de)強對流天氣(qi),是(shi)在強烈(lie)(lie)的(de)(de)不穩定的(de)(de)天氣(qi)狀況下(xia)由空(kong)氣(qi)對流運動造(zao)成的(de)(de)、強烈(lie)(lie)的(de)(de)、小范圍的(de)(de)空(kong)氣(qi)渦旋。
從積(ji)雨(yu)云(yun)中伸(shen)下的(de)猛烈旋轉(zhuan)的(de)漏(lou)斗(dou)狀(zhuang)(zhuang)云(yun)樓(lou)。它有(you)時(shi)(shi)稍伸(shen)即隱,有(you)時(shi)(shi)懸掛空中或(huo)(huo)觸(chu)及地(di)面(mian)(mian)。龍(long)(long)卷(juan)(juan)(juan)風(feng)(feng)漏(lou)斗(dou)云(yun)的(de)軸一(yi)般(ban)垂直(zhi)(zhi)于地(di)面(mian)(mian),在(zai)發展的(de)后期,當上(shang)下層風(feng)(feng)速(su)(su)相差較大(da)時(shi)(shi),可(ke)成(cheng)傾斜狀(zhuang)(zhuang)或(huo)(huo)彎曲狀(zhuang)(zhuang)。其下部直(zhi)(zhi)徑最(zui)小(xiao)的(de)只有(you)幾米,一(yi)般(ban)為(wei)數百米,最(zui)大(da)可(ke)達千米以上(shang),上(shang)部直(zhi)(zhi)徑一(yi)般(ban)為(wei)數千米,最(zui)大(da)可(ke)達10公里(li)。龍(long)(long)卷(juan)(juan)(juan)風(feng)(feng)的(de)尺(chi)度很(hen)小(xiao),中心氣(qi)(qi)(qi)壓很(hen)低,造成(cheng)很(hen)大(da)的(de)水(shui)平氣(qi)(qi)(qi)壓梯度,從而(er)(er)導致強(qiang)(qiang)烈的(de)風(feng)(feng)速(su)(su),中心風(feng)(feng)速(su)(su)可(ke)達100-200米/秒。由于氣(qi)(qi)(qi)流的(de)旋轉(zhuan)力(li)很(hen)強(qiang)(qiang),常(chang)將地(di)面(mian)(mian)的(de)水(shui)、塵土、泥沙挾卷(juan)(juan)(juan)而(er)(er)起(qi)(qi),其破壞力(li)變(bian)動(dong)(dong)范圍(wei)很(hen)大(da),弱者(zhe)僅能卷(juan)(juan)(juan)起(qi)(qi)稻草捆和(或(huo)(huo))衣物強(qiang)(qiang)者(zhe)可(ke)按(an)樹(shu)倒屋,至(zhi)把人、畜也一(yi)并升起(qi)(qi),經過水(shui)面(mian)(mian)時(shi)(shi)可(ke)吸水(shui)上(shang)升如柱(zhu),(這(zhe)時(shi)(shi)稱水(shui)龍(long)(long)卷(juan)(juan)(juan)),所以龍(long)(long)卷(juan)(juan)(juan)風(feng)(feng)范圍(wei)雖小(xiao),但造成(cheng)的(de)災情卻很(hen)嚴(yan)重。龍(long)(long)卷(juan)(juan)(juan)風(feng)(feng)的(de)移(yi)向、移(yi)速(su)(su)是(shi)由其母云(yun)(產生(sheng)龍(long)(long)卷(juan)(juan)(juan)的(de)積(ji)雨(yu)云(yun))的(de)移(yi)動(dong)(dong)決定的(de),母云(yun)的(de)移(yi)速(su)(su)通常(chang)為(wei)每小(xiao)時(shi)(shi)40-50公里(li),最(zui)快可(ke)達90-100公里(li)。其移(yi)動(dong)(dong)路徑多(duo)呈直(zhi)(zhi)線(xian),一(yi)般(ban)只有(you)幾公里(li),個別可(ke)達數十公里(li)。龍(long)(long)卷(juan)(juan)(juan)風(feng)(feng)是(shi)強(qiang)(qiang)對流天(tian)氣(qi)(qi)(qi)的(de)產物,常(chang)發生(sheng)于北緯20-50度地(di)帶(dai)(dai)低層大(da)氣(qi)(qi)(qi)層結具有(you)很(hen)大(da)對流不(bu)穩定的(de)地(di)區,往往與(yu)鋒面(mian)(mian)、氣(qi)(qi)(qi)旋或(huo)(huo)非(fei)熱(re)(re)帶(dai)(dai)性雷暴(bao)相伴隨。登陸后的(de)熱(re)(re)帶(dai)(dai)氣(qi)(qi)(qi)旋移(yi)到(dao)中緯趨(qu)向衰亡時(shi)(shi),也很(hen)易(yi)出(chu)現龍(long)(long)卷(juan)(juan)(juan)風(feng)(feng),有(you)時(shi)(shi)還可(ke)出(chu)現在(zai)熱(re)(re)帶(dai)(dai)地(di)區。根據龍(long)(long)卷(juan)(juan)(juan)風(feng)(feng)產生(sheng)的(de)地(di)區可(ke)分為(wei)陸龍(long)(long)卷(juan)(juan)(juan)(產生(sheng)在(zai)陸地(di)上(shang)空)和水(shui)龍(long)(long)卷(juan)(juan)(juan)(產生(sheng)在(zai)海面(mian)(mian)或(huo)(huo)水(shui)面(mian)(mian)上(shang)空)。龍(long)(long)卷(juan)(juan)(juan)風(feng)(feng)很(hen)難(nan)預報,測(ce)雨(yu)雷達也未曾直(zhi)(zhi)接觀(guan)測(ce)到(dao)過。
龍(long)(long)卷(juan)(juan)風,是(shi)一(yi)種具有(you)一(yi)定破壞力的(de)自然現象(xiang)。一(yi)般情況下,龍(long)(long)卷(juan)(juan)風是(shi)一(yi)種氣旋(xuan)。它在(zai)接觸地面(mian)時(shi),直徑(jing)從幾(ji)米(mi)(mi)(mi)(mi)(mi)到幾(ji)百米(mi)(mi)(mi)(mi)(mi),平(ping)均為250米(mi)(mi)(mi)(mi)(mi)左右(you),最(zui)(zui)大(da)為1000米(mi)(mi)(mi)(mi)(mi)左右(you)。在(zai)空中直徑(jing)可有(you)幾(ji)千米(mi)(mi)(mi)(mi)(mi),最(zui)(zui)大(da)有(you)10千米(mi)(mi)(mi)(mi)(mi)。極大(da)風速每小(xiao)時(shi)可達(da)150千米(mi)(mi)(mi)(mi)(mi)至450千米(mi)(mi)(mi)(mi)(mi),龍(long)(long)卷(juan)(juan)風持續時(shi)間,一(yi)般僅幾(ji)分鐘(zhong),最(zui)(zui)長(chang)不過幾(ji)小(xiao)時(shi)。所到之處萬物遭劫。龍(long)(long)卷(juan)(juan)風漏斗(dou)狀中心由吸起的(de)塵(chen)土和凝(ning)聚的(de)水氣組成可見的(de)“龍(long)(long)嘴(zui)”。在(zai)海洋上(shang)(shang),尤(you)其(qi)是(shi)在(zai)熱帶,類似的(de)景象(xiang)在(zai)發生稱為海上(shang)(shang)龍(long)(long)卷(juan)(juan)風。
龍卷風(feng)通常是極(ji)其(qi)快速(su)的(de)(de)(de),每秒鐘(zhong)100米的(de)(de)(de)風(feng)速(su)不足(zu)為奇,甚(shen)至達(da)到每秒鐘(zhong)175米以(yi)上(shang),比12級臺風(feng)還(huan)要大(da)五(wu)、六倍。風(feng)的(de)(de)(de)范圍(wei)很小,一般直(zhi)徑(jing)只有25~100米,只在極(ji)少(shao)數的(de)(de)(de)情況下(xia)直(zhi)徑(jing)才(cai)達(da)到一公(gong)里以(yi)上(shang);從發生到消失(shi)只有幾分種,最多幾個(ge)小時。
大多數龍(long)卷(juan)(juan)風(feng)在北半球(qiu)(qiu)是(shi)(shi)逆時(shi)針旋轉,在南半球(qiu)(qiu)是(shi)(shi)順時(shi)針,也(ye)有例外情況。卷(juan)(juan)風(feng)形成的確切機理仍在研究中,一般(ban)認為是(shi)(shi)與大氣的劇烈活動(dong)有關。
從19世紀以(yi)來(lai),天(tian)氣預報的準確性大大提高,氣象雷達能夠監測到龍卷風(feng)、颶風(feng)等各種災害風(feng)暴。
龍卷風經過之處,常(chang)會發生拔起大樹、掀翻車輛、摧毀建(jian)筑物(wu)等現象,它往往使成(cheng)片莊(zhuang)稼、成(cheng)萬(wan)株果木(mu)瞬(shun)間被(bei)毀,令(ling)交通中斷,房屋倒(dao)塌,人畜生命和經濟遭受(shou)損失。
龍(long)卷風(feng)這種自然(ran)現象是云(yun)層中(zhong)雷暴(bao)(bao)的(de)產(chan)物,具體的(de)說,龍(long)卷風(feng)就是雷暴(bao)(bao)巨大能量(liang)中(zhong)的(de)一小部分在很(hen)小的(de)區域(yu)內集中(zhong)釋放(fang)的(de)一種形式。
龍卷風的(de)形成可以分(fen)為四個階段(duan):
(1)大氣的不穩定性(xing)產(chan)生強(qiang)烈的上(shang)升氣流(liu),由于急流(liu)中(zhong)的最大過境氣流(liu)的影響,它(ta)被進一步加強(qiang)。
(2)由(you)于(yu)與在(zai)垂直方向上速度和方向均有切變的(de)風相互作用,上升氣流在(zai)對流層(ceng)的(de)中部開始旋(xuan)轉,形成中尺度氣旋(xuan)。
(3)隨著(zhu)中尺度氣旋(xuan)(xuan)向(xiang)地面(mian)發展(zhan)和向(xiang)上伸展(zhan),它本身變細(xi)并增強。同時,一個小(xiao)面(mian)積的增強輔合(he),即(ji)初生的龍卷(juan)在氣旋(xuan)(xuan)內部形成(cheng),產生氣旋(xuan)(xuan)的同樣過程,形成(cheng)龍卷(juan)核心。
(4)龍(long)卷(juan)核(he)心中(zhong)的(de)旋(xuan)轉與氣旋(xuan)中(zhong)的(de)不同,它的(de)強度足以使(shi)龍(long)卷(juan)一直伸展到地面。當發展的(de)渦旋(xuan)到達地面高度時(shi),地面氣壓(ya)急(ji)劇(ju)(ju)下降,地面風(feng)速急(ji)劇(ju)(ju)上升,形成(cheng)龍(long)卷(juan)風(feng)。
龍卷(juan)風(feng)(feng)(feng)發生至消散的(de)時間短,作(zuo)(zuo)用(yong)面積(ji)很小,以至于現(xian)有(you)(you)的(de)探測儀器沒有(you)(you)足夠(gou)的(de)靈敏(min)度(du)來(lai)對龍卷(juan)風(feng)(feng)(feng)進行準(zhun)確的(de)觀(guan)測。相對來(lai)說,多(duo)普(pu)勒(le)(le)(le)雷(lei)(lei)(lei)達是(shi)比(bi)較有(you)(you)效和(he)常用(yong)的(de)一種觀(guan)測儀器。多(duo)普(pu)勒(le)(le)(le)雷(lei)(lei)(lei)達對準(zhun)龍卷(juan)風(feng)(feng)(feng)發出(chu)(chu)的(de)微波(bo)束,微波(bo)信號(hao)被龍卷(juan)風(feng)(feng)(feng)中的(de)碎屑和(he)雨點(dian)反(fan)(fan)(fan)射后重被雷(lei)(lei)(lei)達接(jie)收。如果龍卷(juan)風(feng)(feng)(feng)遠離雷(lei)(lei)(lei)達而去,反(fan)(fan)(fan)射回的(de)微波(bo)信號(hao)頻(pin)(pin)率將向(xiang)(xiang)低頻(pin)(pin)方向(xiang)(xiang)移(yi)動;反(fan)(fan)(fan)之(zhi),如果龍卷(juan)風(feng)(feng)(feng)越來(lai)越接(jie)近雷(lei)(lei)(lei)達,則反(fan)(fan)(fan)射回的(de)信號(hao)將向(xiang)(xiang)高(gao)頻(pin)(pin)方向(xiang)(xiang)移(yi)動。這種現(xian)象被稱為多(duo)普(pu)勒(le)(le)(le)頻(pin)(pin)移(yi)。接(jie)收到信號(hao)后,雷(lei)(lei)(lei)達操作(zuo)(zuo)人員(yuan)就可以通過分析頻(pin)(pin)移(yi)數據,計(ji)算(suan)出(chu)(chu)龍卷(juan)風(feng)(feng)(feng)的(de)速度(du)和(he)移(yi)動方向(xiang)(xiang)。
雙(shuang)(shuang)極化技術(shu)的(de)出現(xian)對(dui)多(duo)普(pu)勒天氣雷達(da)探測中氣旋(xuan)和龍(long)卷(juan)進行了(le)有力的(de)補充(chong),全(quan)面提(ti)升了(le)對(dui)龍(long)卷(juan)微物理(li)特征分(fen)析與預警預報(bao)水(shui)平。①由于多(duo)普(pu)勒天氣雷達(da)對(dui)較小尺(chi)度(du)的(de)龍(long)卷(juan)渦旋(xuan)探測需要具有良好的(de)空(kong)間(jian)分(fen)辨率,然而對(dui)雙(shuang)(shuang)極化探測而言并(bing)不(bu)需要太高(gao)的(de)精度(du)。②雙(shuang)(shuang)極化特征信號不(bu)同于多(duo)普(pu)勒特征信號,由于其(qi)是“各向同性”的(de),所以(yi)并(bing)不(bu)依賴于觀測角度(du)的(de)變化。③當龍(long)卷(juan)在夜(ye)間(jian)發生或被大量降水(shui)包裹著難(nan)以(yi)通過多(duo)普(pu)勒雷達(da)觀測發現(xian)時,雙(shuang)(shuang)極化信息更能有效地將其(qi)識(shi)別。
Wurman設計開發了(le)第一部X波段(duan)移動式快速掃描雷(lei)(lei)達 Rapid DOW,該(gai)雷(lei)(lei)達每(mei)7秒可(ke)以(yi)(yi)完(wan)成(cheng)一次360°的(de)體(ti)掃,在14秒的(de)時間里可(ke)以(yi)(yi)探測到 12個波束范圍的(de)數據,并且其距離分辨率達到11米,更易(yi)于對(dui)龍(long)卷(juan)三(san)維(wei)結構進(jin)行研究。從當前對(dui)龍(long)卷(juan)的(de)探測技術(shu)來看,快速掃描雷(lei)(lei)達在時空尺(chi)度上對(dui)龍(long)卷(juan)觀測獨特優(you)勢(shi)。而(er)美國計劃的(de)下一代天氣雷(lei)(lei)達網絡(luo)也定(ding)位為多功能相控陣雷(lei)(lei)達。所以(yi)(yi)可(ke)見該(gai)技術(shu)未來必將(jiang)成(cheng)為研究該(gai)類天氣的(de)主要(yao)手段(duan)。
多漩(xuan)渦龍(long)卷(juan)風(Multiple vortex)指帶有(you)兩股以上圍繞同(tong)一個中心旋(xuan)轉的漩(xuan)渦的龍(long)卷(juan)風。多漩(xuan)渦結構經(jing)常出現(xian)在劇烈的龍(long)卷(juan)風上,并且這些(xie)小漩(xuan)渦在主龍(long)卷(juan)風經(jing)過的地區上往往會(hui)造成更大的破壞(huai)。
水(shui)(shui)(shui)龍(long)(long)卷(juan)(juan)(juan)(或稱海龍(long)(long)卷(juan)(juan)(juan),英(ying)文:waterspout)可(ke)(ke)以簡單地定義為水(shui)(shui)(shui)上的(de)龍(long)(long)卷(juan)(juan)(juan)風,通常意思是在水(shui)(shui)(shui)上的(de)非超級單體龍(long)(long)卷(juan)(juan)(juan)風。世界各地的(de)海洋(yang)和湖(hu)泊等(deng)都可(ke)(ke)能(neng)出現水(shui)(shui)(shui)龍(long)(long)卷(juan)(juan)(juan)。在美國,水(shui)(shui)(shui)龍(long)(long)卷(juan)(juan)(juan)通常發生(sheng)在美國東南部海岸,尤(you)其(qi)(qi)在佛羅(luo)里達南部和墨(mo)西哥灣。水(shui)(shui)(shui)龍(long)(long)卷(juan)(juan)(juan)雖在定義上是龍(long)(long)卷(juan)(juan)(juan)風的(de)一種,不過其(qi)(qi)破壞(huai)性要比最強(qiang)大(da)的(de)大(da)草原(yuan)龍(long)(long)卷(juan)(juan)(juan)風小,但(dan)是它(ta)們(men)仍然(ran)是相當(dang)危險的(de)。水(shui)(shui)(shui)龍(long)(long)卷(juan)(juan)(juan)能(neng)吹翻小船,毀(hui)壞(huai)船只,當(dang)吹襲陸(lu)地時就有(you)更大(da)的(de)破壞(huai),并奪去生(sheng)命(ming)。當(dang)水(shui)(shui)(shui)龍(long)(long)卷(juan)(juan)(juan)很可(ke)(ke)能(neng)產(chan)生(sheng)或在海岸水(shui)(shui)(shui)域上已(yi)經(jing)看得見的(de)時候,美國國家氣象局(ju)將會經(jing)常發出特(te)殊(shu)的(de)海上警(jing)告,或者當(dang)水(shui)(shui)(shui)龍(long)(long)卷(juan)(juan)(juan)會向陸(lu)地移動時發出龍(long)(long)卷(juan)(juan)(juan)風警(jing)告。
陸(lu)龍(long)卷(英文:landspout,美(mei)國(guo)國(guo)家氣象局稱dust-tube tornado)用以(yi)描述一(yi)種和中尺度氣旋沒有關(guan)聯的龍(long)卷風。陸(lu)龍(long)卷和水龍(long)卷有一(yi)些相同的特點,例如(ru)強度相對較(jiao)弱(ruo)、持續(xu)時(shi)間短、冷凝形(xing)成的漏斗云較(jiao)小且經常不(bu)接觸地面等。雖(sui)然強度相對較(jiao)弱(ruo),但陸(lu)龍(long)卷依然會帶來強風和嚴重破壞。
火(huo)(huo)龍(long)卷(juan)(juan),非常罕(han)見(jian)(jian)(jian)的(de)龍(long)卷(juan)(juan)風(feng)形(xing)態,由陸(lu)龍(long)卷(juan)(juan)與火(huo)(huo)焰(yan)的(de)結合。2010年(nian),位于(yu)南(nan)半球的(de)巴(ba)西遭遇罕(han)見(jian)(jian)(jian)的(de)干旱少(shao)雨天氣,全國(guo)多地燃起了山火(huo)(huo)。8月24日(ri)(ri),巴(ba)西圣保(bao)羅市一(yi)處(chu)火(huo)(huo)點刮起了龍(long)卷(juan)(juan)風(feng),形(xing)成了罕(han)見(jian)(jian)(jian)的(de)火(huo)(huo)焰(yan)龍(long)卷(juan)(juan)風(feng)景觀。龍(long)卷(juan)(juan)風(feng)夾(jia)起火(huo)(huo)焰(yan)高(gao)達數米,像一(yi)條(tiao)巨(ju)大的(de)火(huo)(huo)龍(long)旋轉前(qian)進(jin)。這條(tiao)“火(huo)(huo)龍(long)風(feng)”于(yu)24日(ri)(ri)被拍攝到(dao)。“火(huo)(huo)龍(long)”在燃燒的(de)田野上(shang)飛舞高(gao)約數米高(gao),阻斷(duan)了一(yi)條(tiao)公路。為(wei)了熄滅這條(tiao)“火(huo)(huo)龍(long)”,當地出(chu)動了直升機(ji)。
出現“火龍風”的(de)地區(qu)已經有3個月沒(mei)有下雨。異常(chang)干旱的(de)天氣和強勁(jing)的(de)風勢助長了(le)此(ci)處的(de)火勢。巴西全球電(dian)視臺報道稱,圣保羅(luo)地區(qu)的(de)空(kong)氣干燥程(cheng)度已趕(gan)上了(le)撒哈拉沙漠。
龍(long)卷(juan)風(feng)按它的(de)破壞程度不同,分為0-5增強藤(teng)田(tian)級(ji)數,簡單來說(shuo)就稱為EF級(ji),由1971年芝加哥大學的(de)藤(teng)田(tian)哲也博士所(suo)提(ti)出。
EF0級(ji):風速在65-85英里(li)每小時,約合105-137公里(li)每小時,雖然較(jiao)(jiao)弱,但還(huan)是(shi)足以(yi)把(ba)樹(shu)枝吹斷,把(ba)較(jiao)(jiao)輕的碎(sui)片卷(juan)起來(lai)擊碎(sui)玻璃,一些煙囪會被吹斷。(出(chu)現(xian)幾率極(ji)高,53.5%)
EF1級:風(feng)速在每小時(shi)86-110英里每小時(shi),約合138-177公里每小時(shi),它們可以把屋頂吹走,把活(huo)動板房給吹翻,一些較輕的汽(qi)車會被吹翻或(huo)刮離(li)路面。(出現幾率較高,31.6%)
EF2級:風速在111-135英里每小時,約合178-217公里每小時,它們(men)可以把(ba)(ba)沉重的甘草包吹(chui)出去幾(ji)(ji)百米遠,把(ba)(ba)一(yi)棵(ke)大樹連根拔起,貨車可以刮離(li)路(lu)面。(出現幾(ji)(ji)率中等偏低,10.7%)
EF3級(ji):風速在(zai)136-165英里(li)每小時(shi),約合(he)218-266公里(li)每小時(shi),它們可以把一(yi)輛較(jiao)重汽(qi)車吹翻,樹木被吹離(li)地面(mian),房屋一(yi)大(da)半被毀,火車脫離(li)軌道。(出(chu)現幾率(lv)低(di),3.4%)
EF4級(ji):風速(su)在166-200英里(li)每(mei)小時,約(yue)合267-322公里(li)每(mei)小時,它們可(ke)以把一輛汽(qi)車(che)刮飛,把一幢牢固的房屋夷為平(ping)地,樹(shu)木被刮到幾百米高空。(出現幾率很低(di),0.7%)
EF5級:EF5級風速超(chao)過(guo)每(mei)小(xiao)時200英里(li)每(mei)小(xiao)時,也(ye)(ye)就是(shi)超(chao)過(guo)了322公里(li)每(mei)小(xiao)時,房屋(wu)完(wan)全吹毀,汽車完(wan)全刮飛(fei),路面上(shang)的瀝青也(ye)(ye)會被(bei)刮走,貨車、火車、列車全部脫離地面。(出現(xian)幾率較低偏高,20%—45%)
龍卷(juan)(juan)風并沒(mei)有EF6級(ji)。那是(shi)絕對(dui)不可能的(de),這(zhe)是(shi)根據物理和氣象學(xue)推算(suan)出來的(de),所(suo)以,1999年5月(yue)3日俄克拉荷馬(ma)城的(de)龍卷(juan)(juan)風不是(shi)EF6級(ji),而是(shi)EF5級(ji),但是(shi)電視臺也報(bao)道過當天超過每小時512公里的(de)風速,而且在一個雷達(da)上估測(ce)到了318英(ying)里每小時的(de)大(da)風,這(zhe)就(jiu)表明(ming)龍卷(juan)(juan)風的(de)破壞力量很大(da),不要相信(xin)有EF6級(ji)龍卷(juan)(juan)風,那是(shi)虛構。
除此之外,龍(long)卷(juan)風(feng)還可以分為4個(ge)形狀:
煙囪(cong)龍卷(juan)風:輪(lun)廓直(zhi),比較(jiao)粗壯,強度中等(deng),一(yi)般在EF2—EF4級左右(you)。
繩形龍卷風:纖細(xi),輪廓教彎,強度(du)弱,一(yi)般在EF0—EF2左右。
楔形龍卷風:長度較寬,可達1.5公(gong)里,寬度超過高度,強度強,一般在EF4—EF5左右。
雙胞胎(tai)龍(long)卷風:兩個龍(long)卷風,有(you)的粗(cu),有(you)的細(xi),強度不(bu)定。
全球(qiu)除南(nan)極洲以外的大(da)(da)洲都有龍卷風記錄,龍卷風主要發生在中緯度地區,其中美國發生最為頻繁(fan),堪(kan)稱“龍卷王國”,被稱為“龍卷風之鄉”,其發生的龍卷風約占全球(qiu)龍卷風總數(shu)的75%;其次為加拿大(da)(da);歐洲西部(bu)(bu)和(he)中部(bu)(bu)、中國、孟加拉(la)國、日本、澳大(da)(da)利亞、新西蘭、南(nan)非和(he)阿根廷等國家(jia)或地區龍卷風發生也較為頻繁(fan)。
年(nian)(nian)(nian)(nian)(nian)尺度特征美國(guo)(guo)(guo)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)有(you)(you)(you)1000多個(ge)(1991—2010年(nian)(nian)(nian)(nian)(nian)間,平(ping)(ping)(ping)(ping)均(jun)(jun)為1253個(ge)/年(nian)(nian)(nian)(nian)(nian))。其次為加(jia)拿大(da),記(ji)(ji)錄(lu)(lu)到(dao)(dao)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)平(ping)(ping)(ping)(ping)均(jun)(jun)約(yue)70個(ge)/年(nian)(nian)(nian)(nian)(nian),估計實際(ji)發(fa)生(sheng)(sheng)(sheng)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)平(ping)(ping)(ping)(ping)均(jun)(jun)約(yue)150個(ge)/年(nian)(nian)(nian)(nian)(nian)。歐(ou)洲平(ping)(ping)(ping)(ping)均(jun)(jun)觀測到(dao)(dao)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)大(da)約(yue)有(you)(you)(you)330個(ge)/年(nian)(nian)(nian)(nian)(nian),其中(zhong)陸龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)170個(ge),水(shui)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)160個(ge),而實際(ji)發(fa)生(sheng)(sheng)(sheng)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)大(da)約(yue)有(you)(you)(you)700個(ge)/年(nian)(nian)(nian)(nian)(nian),其中(zhong)陸龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)300個(ge),水(shui)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)390個(ge)。歐(ou)洲龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)多發(fa)生(sheng)(sheng)(sheng)于英國(guo)(guo)(guo)、德國(guo)(guo)(guo)、法國(guo)(guo)(guo)和(he)西班牙:英國(guo)(guo)(guo)(1981—2010年(nian)(nian)(nian)(nian)(nian)間)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)大(da)約(yue)有(you)(you)(you) (47.2±10.5)個(ge)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng),其中(zhong)陸龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(36.5±10.1)個(ge),水(shui)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(12.7±2.8)個(ge);法國(guo)(guo)(guo)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)有(you)(you)(you)15~20個(ge)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)。亞(ya)洲的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)主要發(fa)生(sheng)(sheng)(sheng)在中(zhong)國(guo)(guo)(guo)、日本(ben)、印(yin)度和(he)孟(meng)加(jia)拉國(guo)(guo)(guo):中(zhong)國(guo)(guo)(guo)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)發(fa)生(sheng)(sheng)(sheng)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)有(you)(you)(you)73個(ge);日本(ben)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)發(fa)生(sheng)(sheng)(sheng)20.5個(ge)陸龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)和(he)4.5個(ge)水(shui)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan);孟(meng)加(jia)拉國(guo)(guo)(guo)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)發(fa)生(sheng)(sheng)(sheng)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)有(you)(you)(you)2個(ge)。大(da)洋洲的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)主要發(fa)生(sheng)(sheng)(sheng)在澳大(da)利(li)(li)亞(ya)和(he)新(xin)(xin)西蘭(lan):澳大(da)利(li)(li)亞(ya)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)發(fa)生(sheng)(sheng)(sheng)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)有(you)(you)(you)29個(ge),新(xin)(xin)西蘭(lan)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)發(fa)生(sheng)(sheng)(sheng)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)有(you)(you)(you)17個(ge)。南美洲的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)多發(fa)于阿根廷(ting)中(zhong)部(bu)的(de)(de)潘帕(pa)斯草(cao)原:阿根廷(ting)平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)記(ji)(ji)錄(lu)(lu)到(dao)(dao)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)大(da)概有(you)(you)(you)10個(ge);巴西、智利(li)(li)和(he)烏(wu)拉圭也有(you)(you)(you)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)的(de)(de)記(ji)(ji)錄(lu)(lu),巴西平(ping)(ping)(ping)(ping)均(jun)(jun)每(mei)(mei)(mei)(mei)(mei)年(nian)(nian)(nian)(nian)(nian)記(ji)(ji)錄(lu)(lu)到(dao)(dao)的(de)(de)龍(long)(long)(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)(feng)有(you)(you)(you)3個(ge)。
美國(guo)(guo)的(de)(de)(de)(de)龍(long)卷(juan)風(feng)多(duo)(duo)發(fa)(fa)(fa)(fa)(fa)于春季,其(qi)(qi)次為(wei)(wei)(wei)夏(xia)(xia)季,冬季最(zui)(zui)(zui)少發(fa)(fa)(fa)(fa)(fa)生(sheng)。歐(ou)洲(zhou)的(de)(de)(de)(de)龍(long)卷(juan)風(feng)主(zhu)要(yao)發(fa)(fa)(fa)(fa)(fa)生(sheng)在(zai)(zai)夏(xia)(xia)季,其(qi)(qi)次為(wei)(wei)(wei)秋(qiu)季:英國(guo)(guo)龍(long)卷(juan)風(feng)主(zhu)要(yao)發(fa)(fa)(fa)(fa)(fa)生(sheng)在(zai)(zai)秋(qiu)季(9—11月(yue)(yue)(yue)(yue)(yue)),其(qi)(qi)次為(wei)(wei)(wei)夏(xia)(xia)季(6—8月(yue)(yue)(yue)(yue)(yue)),11月(yue)(yue)(yue)(yue)(yue)為(wei)(wei)(wei)龍(long)卷(juan)風(feng)發(fa)(fa)(fa)(fa)(fa)生(sheng)最(zui)(zui)(zui)多(duo)(duo)月(yue)(yue)(yue)(yue)(yue);德國(guo)(guo)2/3的(de)(de)(de)(de)龍(long)卷(juan)風(feng)發(fa)(fa)(fa)(fa)(fa)生(sheng)在(zai)(zai)6—8月(yue)(yue)(yue)(yue)(yue),其(qi)(qi)中7月(yue)(yue)(yue)(yue)(yue)龍(long)卷(juan)風(feng)發(fa)(fa)(fa)(fa)(fa)生(sheng)頻(pin)率達27%;法(fa)國(guo)(guo)的(de)(de)(de)(de)龍(long)卷(juan)風(feng)多(duo)(duo)發(fa)(fa)(fa)(fa)(fa)于春季和夏(xia)(xia)季,8月(yue)(yue)(yue)(yue)(yue)發(fa)(fa)(fa)(fa)(fa)生(sheng)最(zui)(zui)(zui)多(duo)(duo);西班牙(ya)的(de)(de)(de)(de)龍(long)卷(juan)風(feng)多(duo)(duo)發(fa)(fa)(fa)(fa)(fa)于暖季,明顯的(de)(de)(de)(de)趨向于秋(qiu)季。澳大利亞的(de)(de)(de)(de)龍(long)卷(juan)風(feng)多(duo)(duo)發(fa)(fa)(fa)(fa)(fa)于初春和夏(xia)(xia)季,其(qi)(qi)次為(wei)(wei)(wei)初冬。中國(guo)(guo)龍(long)卷(juan)風(feng)發(fa)(fa)(fa)(fa)(fa)生(sheng)的(de)(de)(de)(de)季節變(bian)化特(te)征明顯,主(zhu)要(yao)集中在(zai)(zai)春夏(xia)(xia)兩季,尤(you)以7月(yue)(yue)(yue)(yue)(yue)和8月(yue)(yue)(yue)(yue)(yue)最(zui)(zui)(zui)多(duo)(duo),兩月(yue)(yue)(yue)(yue)(yue)約占全年總數(shu)的(de)(de)(de)(de)50%以上。日本56%的(de)(de)(de)(de)陸(lu)龍(long)卷(juan)發(fa)(fa)(fa)(fa)(fa)生(sheng)在(zai)(zai)7—10月(yue)(yue)(yue)(yue)(yue),其(qi)(qi)中9月(yue)(yue)(yue)(yue)(yue)最(zui)(zui)(zui)為(wei)(wei)(wei)頻(pin)繁,3月(yue)(yue)(yue)(yue)(yue)最(zui)(zui)(zui)少;水龍(long)卷(juan)主(zhu)要(yao)發(fa)(fa)(fa)(fa)(fa)生(sheng)在(zai)(zai)9—10月(yue)(yue)(yue)(yue)(yue),10月(yue)(yue)(yue)(yue)(yue)最(zui)(zui)(zui)多(duo)(duo)。
美國(guo)的佛羅里達州(zhou)和(he)中(zhong)(zhong)(zhong)(zhong)(zhong)南(nan)(nan)(nan)(nan)部(bu)(bu)(bu)(bu)平(ping)(ping)原(yuan)(yuan)是龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)的高發區(qu),中(zhong)(zhong)(zhong)(zhong)(zhong)南(nan)(nan)(nan)(nan)部(bu)(bu)(bu)(bu)平(ping)(ping)原(yuan)(yuan)稱為(wei)“龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)走(zou)廊”,其(qi)范圍一般(ban)(ban)指(zhi)從德克(ke)薩(sa)(sa)斯州(zhou)中(zhong)(zhong)(zhong)(zhong)(zhong)部(bu)(bu)(bu)(bu)向北(bei)(bei)(bei)(bei)(bei)到愛荷華州(zhou)北(bei)(bei)(bei)(bei)(bei)部(bu)(bu)(bu)(bu),以(yi)及從堪薩(sa)(sa)斯州(zhou)中(zhong)(zhong)(zhong)(zhong)(zhong)部(bu)(bu)(bu)(bu)和(he)內(nei)布(bu)拉斯加(jia)東(dong)部(bu)(bu)(bu)(bu)到俄亥俄西(xi)部(bu)(bu)(bu)(bu)的區(qu)域(yu)(yu)。英國(guo)的龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)主(zhu)要發生(sheng)于英格蘭(lan)的東(dong)部(bu)(bu)(bu)(bu)和(he)南(nan)(nan)(nan)(nan)部(bu)(bu)(bu)(bu)以(yi)及海(hai)峽群島周邊。德國(guo)的龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)多(duo)(duo)發于沿(yan)海(hai)和(he)丘陵地區(qu)。法(fa)國(guo)的龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)多(duo)(duo)發于西(xi)北(bei)(bei)(bei)(bei)(bei)部(bu)(bu)(bu)(bu)、南(nan)(nan)(nan)(nan)部(bu)(bu)(bu)(bu)和(he)東(dong)部(bu)(bu)(bu)(bu)。西(xi)班牙的龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)多(duo)(duo)發于地中(zhong)(zhong)(zhong)(zhong)(zhong)海(hai)區(qu)域(yu)(yu)和(he)加(jia)的斯灣附近(jin)省(sheng)(sheng)(sheng)(sheng)份。中(zhong)(zhong)(zhong)(zhong)(zhong)國(guo)龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)一般(ban)(ban)多(duo)(duo)發生(sheng)在(zai)中(zhong)(zhong)(zhong)(zhong)(zhong)東(dong)部(bu)(bu)(bu)(bu)地形相對平(ping)(ping)坦的平(ping)(ping)原(yuan)(yuan)地區(qu),平(ping)(ping)原(yuan)(yuan)多(duo)(duo)于山區(qu);從區(qu)域(yu)(yu)尺(chi)度來看(kan)(kan),長(chang)江三角洲(zhou)、蘇(su)北(bei)(bei)(bei)(bei)(bei)、魯西(xi)南(nan)(nan)(nan)(nan)、豫(yu)東(dong)等平(ping)(ping)原(yuan)(yuan)、湖(hu)沼區(qu)以(yi)及雷州(zhou)半(ban)島等地都(dou)是龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)的易發區(qu);從省(sheng)(sheng)(sheng)(sheng)級行政(zheng)單元尺(chi)度來看(kan)(kan),江蘇(su)省(sheng)(sheng)(sheng)(sheng)、安(an)徽省(sheng)(sheng)(sheng)(sheng)、廣東(dong)省(sheng)(sheng)(sheng)(sheng)、河南(nan)(nan)(nan)(nan)省(sheng)(sheng)(sheng)(sheng)、湖(hu)北(bei)(bei)(bei)(bei)(bei)省(sheng)(sheng)(sheng)(sheng)是龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)多(duo)(duo)發的省(sheng)(sheng)(sheng)(sheng)份,黑龍(long)(long)(long)江省(sheng)(sheng)(sheng)(sheng)、河北(bei)(bei)(bei)(bei)(bei)省(sheng)(sheng)(sheng)(sheng)、浙江省(sheng)(sheng)(sheng)(sheng)、江西(xi)省(sheng)(sheng)(sheng)(sheng)和(he)湖(hu)南(nan)(nan)(nan)(nan)省(sheng)(sheng)(sheng)(sheng)等省(sheng)(sheng)(sheng)(sheng)份龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)的發生(sheng)頻次較高。1961—1993年間日本的陸龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)和(he)水(shui)龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)主(zhu)要發生(sheng)在(zai)沿(yan)海(hai)地區(qu),而關東(dong)地區(qu)大量龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)遠離(li)沿(yan)海(hai)區(qu)域(yu)(yu)。大洋洲(zhou)的龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)主(zhu)要發生(sheng)在(zai)澳大利亞(ya)和(he)新西(xi)蘭(lan)。澳大利亞(ya)的龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)主(zhu)要發生(sheng)于東(dong)南(nan)(nan)(nan)(nan)部(bu)(bu)(bu)(bu)和(he)西(xi)南(nan)(nan)(nan)(nan)部(bu)(bu)(bu)(bu)。南(nan)(nan)(nan)(nan)美洲(zhou)的龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)風(feng)(feng)(feng)多(duo)(duo)發于阿根廷中(zhong)(zhong)(zhong)(zhong)(zhong)部(bu)(bu)(bu)(bu)的潘帕斯草原(yuan)(yuan)。巴西(xi)龍(long)(long)(long)卷(juan)(juan)(juan)(juan)(juan)(juan)多(duo)(duo)發于南(nan)(nan)(nan)(nan)部(bu)(bu)(bu)(bu)和(he)東(dong)南(nan)(nan)(nan)(nan)部(bu)(bu)(bu)(bu)。
我(wo)(wo)國大部分省(區、市)都有龍卷(juan)(juan)風的(de)蹤(zong)跡,主要發生(sheng)在(zai)我(wo)(wo)國東部平原地(di)區,1991年(nian)-2014年(nian),我(wo)(wo)國平均(jun)每年(nian)有43個龍卷(juan)(juan)風,其中江蘇和(he)(he)廣東最(zui)多(duo),年(nian)均(jun)龍卷(juan)(juan)風分別為5.5個和(he)(he)4.8個。春季、夏季是龍卷(juan)(juan)風的(de)多(duo)發季節,4-8月龍卷(juan)(juan)風占全(quan)年(nian)的(de)92%。
龍卷(juan)風(feng)是一(yi)種破壞力極(ji)強的(de)(de)小尺度天(tian)氣(qi)(qi)現象,直徑一(yi)般在100米(mi)以(yi)下,強龍卷(juan)可達幾(ji)百米(mi)到(dao)1千(qian)米(mi)左右。相比于臺風(feng)、副高(gao)這些天(tian)氣(qi)(qi)系(xi)統中的(de)(de)“大塊(kuai)頭”,龍卷(juan)風(feng)絕(jue)對(dui)屬(shu)于“小個子”。而當前(qian)我們(men)的(de)(de)氣(qi)(qi)象臺站不(bu)夠密集,以(yi)至于龍卷(juan)風(feng)經常躲過氣(qi)(qi)象監測(ce)的(de)(de)“法眼”。
龍卷(juan)風(feng)強對(dui)(dui)流天氣(qi)往(wang)往(wang)生成很突然,對(dui)(dui)某(mou)一(yi)地區的(de)影響時(shi)間也相對(dui)(dui)較短,“生命史(shi)”只(zhi)有十幾分鐘(zhong)到個把小(xiao)時(shi)。因此,要提前24小(xiao)時(shi)或(huo)是48小(xiao)時(shi)預報局(ju)部(bu)地區的(de)強對(dui)(dui)流天氣(qi)也就(jiu)非常困難(nan)了。
龍卷風等強對流(liu)天氣的(de)生成和發展需(xu)要衡量綜合大氣條件(jian),而這些條件(jian)往(wang)往(wang)是(shi)難以(yi)預料(liao)、不確切的(de),再加上不同地區(qu)之間(jian)各(ge)不相同的(de)地形因(yin)素(su),也進一步增加了準確監測、預報的(de)難度。
(1)龍卷(juan)(juan)風(feng)發生是(shi)(shi)(shi)和(he)強烈發展的(de)(de)(de)(de)積雨云(yun)聯系在一(yi)起(qi)的(de)(de)(de)(de),也就是(shi)(shi)(shi)通(tong)常所(suo)(suo)說的(de)(de)(de)(de)雷(lei)雨云(yun)。龍卷(juan)(juan)風(feng)出(chu)現時(shi)天(tian)(tian)空往往烏天(tian)(tian)黑地(di)(云(yun)層低而深(shen)厚、亮(liang)度差)、電閃雷(lei)鳴、風(feng)雨交加。以春未到秋初最常見,在一(yi)天(tian)(tian)中以下(xia)午至傍晚(wan)和(he)凌(ling)晨(chen)至早(zao)晨(chen)出(chu)現最多。當看到天(tian)(tian)空有類似(si)的(de)(de)(de)(de)癥兆就要(yao)引起(qi)注意(yi)。人群(qun)應(ying)立刻(ke)離開(kai)危險房(fang)屋、活動場所(suo)(suo)或(huo)(huo)其他簡易臨時(shi)住處,到附近比較堅固的(de)(de)(de)(de)房(fang)屋內躲(duo)(duo)避。在公共場所(suo)(suo),要(yao)服從指揮(hui),有秩序地(di)向指定地(di)點疏散。躲(duo)(duo)避龍卷(juan)(juan)風(feng)最為(wei)安全的(de)(de)(de)(de)地(di)方是(shi)(shi)(shi)位于地(di)下(xia)的(de)(de)(de)(de)空間或(huo)(huo)場所(suo)(suo)(如地(di)下(xia)室或(huo)(huo)半地(di)下(xia)室),地(di)面(mian)上所(suo)(suo)有建(jian)筑物此時(shi)都不(bu)是(shi)(shi)(shi)安全躲(duo)(duo)避的(de)(de)(de)(de)場所(suo)(suo)。
(2)在(zai)野外(wai)遇(yu)到龍卷風(feng)襲擊時,不必驚慌失措,應(ying)迅(xun)速(su)朝龍卷風(feng)移(yi)動(dong)方向(xiang)的垂(chui)直方向(xiang)跑動(dong),伏于低洼(wa)地(di)面、溝渠等(deng)(deng),但要遠離大樹、電線桿、廣告牌、圍(wei)墻等(deng)(deng),以免(mian)被(bei)砸(za)、被(bei)壓或發生觸電事故。如(ru)在(zai)汽車中,應(ying)及時離開(kai),到低洼(wa)地(di)躲避,因為汽車本(ben)身沒有防御(yu)龍卷風(feng)能力,一旦汽車和人(ren)同時被(bei)龍卷風(feng)卷起,危害更大。
(3)在家遇到(dao)(dao)龍(long)卷風(feng)(feng)時(shi),遠離和龍(long)卷風(feng)(feng)同(tong)方向(xiang)的(de)(de)窗、門、房屋的(de)(de)外圍墻(qiang)壁,盡可(ke)能(neng)在龍(long)卷風(feng)(feng)相反方向(xiang)角落或(huo)(huo)比較堅(jian)固的(de)(de)小(xiao)房間抱頭蹲下,保(bao)護好自(zi)己的(de)(de)頭部。在樓(lou)(lou)上,特別是農村的(de)(de)樓(lou)(lou)房內(nei),應立即暫(zan)避到(dao)(dao)一樓(lou)(lou)比較堅(jian)固的(de)(de)桌子底下或(huo)(huo)廁所、儲物間內(nei)。這(zhe)是因(yin)為(wei)龍(long)卷風(feng)(feng)中心的(de)(de)氣壓極低(di),容(rong)易被龍(long)卷風(feng)(feng)外吸、房屋倒(dao)塌而殃及室內(nei)人員(yuan)安(an)全(quan)。
(4)在(zai)遭(zao)遇龍卷風(feng)和發(fa)生(sheng)(sheng)房屋(wu)倒(dao)塌、電(dian)(dian)桿折斷的(de)情(qing)況(kuang)下,應及時(shi)切斷電(dian)(dian)源(yuan),以防(fang)觸電(dian)(dian)和引(yin)發(fa)火災事故。如果是化工生(sheng)(sheng)產企(qi)業遭(zao)受龍卷風(feng)襲擊,應及時(shi)關閉有毒化學(xue)物品(pin)閥門,控制化學(xue)物品(pin)泄漏(lou),防(fang)止污(wu)染源(yuan)向土壤和水面擴散,必要時(shi)組織附(fu)近(jin)市(村)民緊急(ji)轉移。
(5)龍卷(juan)風(feng)后(hou)自(zi)救(jiu)互救(jiu)。由于龍卷(juan)風(feng)的(de)風(feng)力特(te)別大(da),具有巨大(da)的(de)破壞(huai)作用(yong),龍卷(juan)經過的(de)區(qu)域內,房屋等(deng)建筑物常會遭受不(bu)(bu)同程度的(de)破壞(huai),甚至發生(sheng)倒塌。因此,受龍卷(juan)影(ying)響(xiang)地區(qu)的(de)群眾,尤其(qi)是家庭、鄰里之(zhi)間(jian)在災后(hou)第一時(shi)(shi)間(jian)的(de)自(zi)救(jiu)互救(jiu)可最大(da)限(xian)度減少人員(yuan)傷亡。被(bei)埋壓(ya)人員(yuan)要(yao)保(bao)持清醒頭腦,盡快想法(fa)脫離險境,如果不(bu)(bu)能自(zi)我脫險時(shi)(shi),應(ying)盡量創造(zao)和擴大(da)安(an)全生(sheng)存空(kong)間(jian),減少對身體(ti)(ti)的(de)擠壓(ya),特(te)別是對腹部(bu)以上(shang)身體(ti)(ti)部(bu)位的(de)壓(ya)物要(yao)清除(chu)或(huo)移開,加強(qiang)對頭部(bu)及口、鼻等(deng)器官的(de)自(zi)我保(bao)護(hu),等(deng)待救(jiu)援。救(jiu)援時(shi)(shi)要(yao)講究方法(fa),首先應(ying)使被(bei)救(jiu)者(zhe)暴露頭部(bu),保(bao)持呼吸暢通,如有窒息,應(ying)立(li)即進行人工呼吸。其(qi)次不(bu)(bu)可生(sheng)拉(la)硬扯或(huo)使用(yong)利器硬挖被(bei)埋者(zhe),以免造(zao)成進一步的(de)損傷,同時(shi)(shi)對傷重者(zhe)及時(shi)(shi)送(song)醫(yi)院搶救(jiu)。